MergeResult.java

/*
 * Copyright (C) 2009, Christian Halstrick <christian.halstrick@sap.com> and others
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Distribution License v. 1.0 which is available at
 * https://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

package org.eclipse.jgit.merge;

import java.util.Iterator;
import java.util.List;

import org.eclipse.jgit.diff.Sequence;
import org.eclipse.jgit.merge.MergeChunk.ConflictState;
import org.eclipse.jgit.util.IntList;

/**
 * The result of merging a number of {@link org.eclipse.jgit.diff.Sequence}
 * objects. These sequences have one common predecessor sequence. The result of
 * a merge is a list of MergeChunks. Each MergeChunk contains either a range (a
 * subsequence) from one of the merged sequences, a range from the common
 * predecessor or a conflicting range from one of the merged sequences. A
 * conflict will be reported as multiple chunks, one for each conflicting range.
 * The first chunk for a conflict is marked specially to distinguish the border
 * between two consecutive conflicts.
 * <p>
 * This class does not know anything about how to present the merge result to
 * the end-user. MergeFormatters have to be used to construct something human
 * readable.
 *
 * @param <S>
 *            type of sequence.
 */
public class MergeResult<S extends Sequence> implements Iterable<MergeChunk> {
    private final List<S> sequences;

    final IntList chunks = new IntList();

    private boolean containsConflicts = false;

    /**
     * Creates a new empty MergeResult
     *
     * @param sequences
     *            contains the common predecessor sequence at position 0
     *            followed by the merged sequences. This list should not be
     *            modified anymore during the lifetime of this
     *            {@link org.eclipse.jgit.merge.MergeResult}.
     */
    public MergeResult(List<S> sequences) {
        this.sequences = sequences;
    }

    /**
     * Adds a new range from one of the merged sequences or from the common
     * predecessor. This method can add conflicting and non-conflicting ranges
     * controlled by the conflictState parameter
     *
     * @param srcIdx
     *            determines from which sequence this range comes. An index of
     *            x specifies the x+1 element in the list of sequences
     *            specified to the constructor
     * @param begin
     *            the first element from the specified sequence which should be
     *            included in the merge result. Indexes start with 0.
     * @param end
     *            specifies the end of the range to be added. The element this
     *            index points to is the first element which not added to the
     *            merge result. All elements between begin (including begin) and
     *            this element are added.
     * @param conflictState
     *            when set to NO_CONLICT a non-conflicting range is added.
     *            This will end implicitly all open conflicts added before.
     */
    public void add(int srcIdx, int begin, int end, ConflictState conflictState) {
        chunks.add(conflictState.ordinal());
        chunks.add(srcIdx);
        chunks.add(begin);
        chunks.add(end);
        if (conflictState != ConflictState.NO_CONFLICT)
            containsConflicts = true;
    }

    /**
     * Returns the common predecessor sequence and the merged sequence in one
     * list. The common predecessor is the first element in the list
     *
     * @return the common predecessor at position 0 followed by the merged
     *         sequences.
     */
    public List<S> getSequences() {
        return sequences;
    }

    static final ConflictState[] states = ConflictState.values();

    /** {@inheritDoc} */
    @Override
    public Iterator<MergeChunk> iterator() {
        return new Iterator<MergeChunk>() {
            int idx;

            @Override
            public boolean hasNext() {
                return (idx < chunks.size());
            }

            @Override
            public MergeChunk next() {
                ConflictState state = states[chunks.get(idx++)];
                int srcIdx = chunks.get(idx++);
                int begin = chunks.get(idx++);
                int end = chunks.get(idx++);
                return new MergeChunk(srcIdx, begin, end, state);
            }

            @Override
            public void remove() {
                throw new UnsupportedOperationException();
            }
        };
    }

    /**
     * Whether this merge result contains conflicts
     *
     * @return true if this merge result contains conflicts
     */
    public boolean containsConflicts() {
        return containsConflicts;
    }

    /**
     * Sets explicitly whether this merge should be seen as containing a
     * conflict or not. Needed because during RecursiveMerger we want to do
     * content-merges and take the resulting content (even with conflict
     * markers!) as new conflict-free content
     *
     * @param containsConflicts
     *            whether this merge should be seen as containing a conflict or
     *            not.
     * @since 3.5
     */
    protected void setContainsConflicts(boolean containsConflicts) {
        this.containsConflicts = containsConflicts;
    }
}